Prior art centrifuge rotors have incorporated designs which have permanently mounted rings, interspaced and pivotable between radial arms extending from the turning axis of a centrifuge rotor. Generally, the rings provide a means for supporting a sample container such as a test tube, in a generally vertical free-hanging position during non-operative periods of the centrifuge and for allowing the test tube to swing to a generally horizontal position under an applied centrifugal force field generated when the rotor is turned at high rotational speed. The extending arms supporting a pivotable ring are generally formed radially outwardly from a yoke portion central to the rotor. Pin means are provided, either extending outwardly from the ring into receiving bores formed in the extending arms or vice versa, from the arms to bores in the ring.
Prior art designs as described above, are limited in their ability to survive catastrophic failure under increasing centrifugal forces generally by the design of the extending arms or the pivotable connection between the arms and the ring. When the support pin for mounting a ring is formed as an integral part of either the ring or the extending arm, stresses are caused whenever there is a surface irregularity by application of the high centrifugal forces, resulting in an initial cracking and, finally, destructive failure of either the arm or the ring. Attempts to strengthen these parts to broaden the magnitude of force under which these parts can survive have met with limited success, generally due to design limitations on the size of the parts. For instance, sizing the extending arm in larger proportions or making the arm out of a stronger material such as high-strength steel, which is heavier in weight, leads to even greater strength requirements due to the increased mass of the part which is affected by the centrifugal force field. Thus, simply increasing the size or using a stronger but heavier material in forming the extending arms, or any of the outwardly extended part such as the rings, does not assure increased performance capability permitting the rotor to generate higher centrifugal force fields without failure.